Producing a polarized laser beam with minimum divergence and a desired spatial cross-section

Abstract

A system for polarizing laser light produces a polarized laser beam with a desired spatial cross-section and minimum divergence. Optical fibers emitting laser light are configured to a chosen spatial cross-section. The emitted laser light is split into two beams that are polarized. The spatial cross-section of one of the beams are combined so that they are aligned and contiguous.

The Invention claimed is:  
     
         1 . A method for producing a polarized laser beam with minimum divergence and a desired spatial cross-section, comprising: 
 emitting a laser beam from optical fibers;    configuring the optical fibers with a spatial cross-section in a shape that is one-half the shape of the desired cross-section;    splitting the laser beam emitted from the configured optical fibers into a first component beam with a spatial cross-section and a second components beam with a spatial cross-section;    circularly polarizing the first and second component beams;    focusing the first and second component beams at a focal point;    inverting the spatial cross-section of one of the component beams compared to the spatial cross-section of the other component beam; and    combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.    
     
     
         2 . A system for producing a polarized laser beam with minimum divergence and a desired spatial cross-section, comprising: 
 optical fibers emitting a laser beam configured with a spatial cross-section in a shape that is one-half the shape of the desired cross-section;    means for splitting the laser beam emitted from the configured optical fibers into a first component beam with a spatial cross-section and a second component beam with a spatial cross-section;    means for circularly polarizing the first and second component beams;    means for focusing the first and second component beams at a focal point;    means for inverting the spatial cross-section of one of the component beams compared to the spatial cross-section of the other component beam; and    means for combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.    
     
     
         3 . The system of  claim 2  wherein the means for splitting the laser beam comprises a beam-splitter polarizing cube.  
     
     
         4 . The system of  claim 2  wherein the means for polarizing the first and second component beams comprises two quarter wave plates, positioned with a fast axis of either +45° or −45° relative to the vertical so an to achieve the desired direction of circular polarization.  
     
     
         5 . The system of  claim 2  wherein the means for focusing the first and second component beams are two converging lenses with common focal lengths.  
     
     
         6 . The system of  claim 2  wherein the means for inverting the spatial cross-section of one of the component beams compared to the spatial cross-section of the other component beam is a mirror.  
     
     
         7 . The system of  claim 2  wherein the means for combining the first and second component beams is a mirror.  
     
     
         8 . The system of  claim 2  wherein the means for combining the first and second component beams is a prism.  
     
     
         9 . A system for producing a polarized laser beam with minimum divergence and a desired spatial cross-section, comprising: 
 optical fibers emitting a laser beam configured with a spatial cross-section that is one-half the desired cross-section;    a polarizing cube for splitting the laser beam into a first component beam and a second component beam;    two quarter wave plates positioned with a fast axis of +45° or −45° relative to the vertical so as to achieve the desired direction of circular polarization;    a first converging lens for focusing the first component beam at a focal point and a second converging lens with a common focal length with the first converging lens for focusing the second component beam of at the focal point;    a mirror for inverting the spatial cross-section of one of the component beams compared to the spatial cross-section of the other component beam; and    a mirror for combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.    
     
     
         10 . A system for producing a polarized laser beam with minimum divergence and a desired spatial cross-section, comprising: 
 optical fibers emitting a laser beam configured with a spatial cross-section in a shape that is one-half the shape of the desired cross-section;    means for splitting the laser beam emitted from the configured optical fibers into a first component beam with a spatial cross-section and a second component beam with a spatial cross-section;    means for linearly polarizing in the same plane the first and second component beams;    means for focusing the first and second component beams at a focal point;    means for inverting the spatial cross-section of one of the component beams compared to the spatial cross-section of the other component beam; and    means for combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.    
     
     
         11 . A method for producing a polarized laser beam with minimum divergence, comprising: 
 emitting a laser beam from optical fibers;    splitting the laser beam emitted from the configured optical fibers into a first component beam with a spatial cross-section and a second components beam with a spatial cross-section;    circularly polarizing the first and second component beams;    focusing the first and second component beams at a focal point; and    combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.    
     
     
         12 . A system for producing a polarized laser beam with minimum divergence, comprising: 
 optical fibers emitting a laser beam;    means for splitting the laser beam emitted from the configured optical fibers into a first component beam with a spatial cross-section and a second component beam with a spatial cross-section;    means for circularly polarizing the first and second component beams;    means for focusing the first and second component beams at a focal point; and    means for combining the first and second component beams at or near the focal point so that they are aligned and contiguous or nearly contiguous.